Placenta
Nonneoplastic placental conditions and abnormalities
Noninfectious
Meconium staining
Author: Mandolin S. Ziadie, M.D.
Last author update: 1 October 2011
Last staff update: 29 October 2020
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Meconium staining placenta
Table of Contents
Etiology | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) imagesCite this page: Ziadie MS. Meconium staining. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentameconium.html. Accessed June 4th, 2023.
Etiology
- Passage of meconium in utero is due to bowel peristalsis and relaxation of anal sphincter and may be indicative of fetal distress
- Meconium components diffuse into placenta and cord, leading to vasoconstriction and hypoperfusion; damage to fetus increases with length of exposure
- Neonates are at risk for meconium aspiration
- Meconium is unlikely in fetuses prior to 30 weeks gestation
Gross description
- Green brown discoloration of the cord, fetal surface and membranes: differentiate between deposition of slimy green meconium across placental surface that is washed off with a gentle rinse (normal fetus that passes meconium shortly after delivery) and true mecomium staining (exposure to meconium for several hours)
- Membranes may be edematous or slimy
Gross images
Images hosted on other servers:
Green black meconium
Microscopic (histologic) description
- Vacuolation of the amnionic epithelium, edema of the soft tissue plane between the amnion and chorion and pigment laden macrophages within the amnion and chorion
- Prior to 34 weeks, pigment in the membranes is usually hemosiderin
- When prolonged, exposure to meconium can lead to necrosis of individual myocytes in the umbilical and chorionic plate vessels (meconium induced vascular necrosis); this finding increases the risk of neurologic sequelae
- Mild: superficial necrotic or sloughed amniotic epithelium with meconium containing macrophages confined to the surface
- Moderate: ballooning of vacuolated amniotic epithelium with obvious meconium containing macrophages adjacent to chorionic tissue; indicates meconium discharge at least 2 - 3 hours before delivery
- Severe: moderate histologic findings but with more macrophages; may have meconium induced necrosis of umbilical vessels with myocyte necrosis; indicates fetal meconium discharge 6 - 12 hours before delivery
- Associated chorioamnionitis may be present but is not caused by meconium
Microscopic (histologic) images
Images hosted on other servers:
Macrophages
